Controllable exhaust gas turbocharger with a double-fluted turbine housing

ABSTRACT

An exhaust gas-driven turbocharger ( 1 ) exhibits an adjustable radial turbine ( 2 ) which powers a compressor ( 3 ) by way of a common shaft ( 4 ), whereby a turbine housing ( 5 ) designed with a multiplicity of scrolls surround the turbine wheel ( 6 ) and exhibits at least two afflux ports ( 7   a   , 7   b ) annularly encompassing the turbine wheel ( 6 ), whose outlets ( 8   a   , 8   b ) at least partly surround the wheel approach ( 9 ) of the turbine wheel ( 6 ) and which are at an axial distance from one another. An annular, axially displaceable coupler ( 15 ) is provided for opening and closing the outlet ( 8   a   , 8   b ) of at least one afflux port ( 7   a   , 7   b ), so that the boost pressure of the turbine can be influenced thereby.

The present invention relates to an exhaust gas-driven turbo-charger asclaimed in claim 1. Such an exhaust gas-driven turbo-charger is knownfrom the publication 'Kraftfahrtechnisches Taschenbuch/Bosch' (Pocketbook on motor vehicle technology), 21st edition, 1991, page 420 ff.

In exhaust gas-driven turbo-chargers for passenger car engines it isnecessary to provide a control of the exhaust gas-driven turbo-chargerin order to achieve a near constant boost pressure in the widestpossible speed range as a result of the large speed range in passengercar engines. According to the prior art, a control on the exhaust gasside is known in which a portion of the exhaust gas from the engine isguided past the turbine (bypass). The control member required for thispurpose can be arranged as a valve or flap. The required controlpressure is tapped on the pressure side in the exhaust gas-driventurbo-charger, such that the system of the exhaust gas-driventurbo-charger with the boost pressure control member represents anindependent unit.

An energetically more favourable control allows the variable turbinegeometry, with which the back pressure behavior of the turbine ischarged continuously and thus the entire exhaust gas energy can be used.

From the known embodiments, adjustable guide blades have becomegenerally accepted due to their considerable control range withsimultaneously favourable efficiency levels. As a result of the rotarymovement of an adjusting ring it is possible to perform an adjustment ofthe blade angle in a very simple manner. The blades are set to thedesired angle either by way of twist cams or directly by way ofadjusting levers attached to the blades. Triggering occurs pneumaticallyby way of an adjusting dashpot with overpressure or underpressure. Amicroelectronic control can appropriately utilise the advantages ofvariable turbine geometry by optimal adaptation of the boost pressureover the entire motor diagram.

A variable turbine geometry (VTG), however, constitutes a considerablecost factor, so that in small engines with a smaller piston capacityturbo-chargers with VTG were unable to be generally established.

On the basis of the aforementioned, it is the object of the presentinvention to provide an exhaust gas-driven turbo-charger of theabovementioned type, which can be used at low cost for smaller engineswith a controllable boost pressure.

This object is achieved according to the present invention by thefeatures of claim 1.

The advantage of the invention is that in contrast to exhaust gas-driventurbo-chargers with variable turbine geometry no complex adjustingmechanisms are provided which control the direction and the speed of theexhaust gas flow prior to wheel approach, but that instead theadjustment of the turbine throughput is performed by way of amulti-fluted turbine housing, whereby a second afflux port can beswitched on successively by means of the coupler. Impacting of theturbine with exhaust gas can accordingly be influenced by means of asimple, annular coupler directly through opening and closing of anafflux port.

A further advantage is that compared to exhaust gas-driven turbo-chargerhaving variable turbine geometry, in which the highest efficiency isachieved only with approximately 50% of the maximum exhaust gas current,in the case of the exhaust gas-driven turbo-charger according to thepresent invention the highest efficiency occurs with minimal mass flow,that is, with minimal engine speed. This leads to improvement in theengine torque in the lower rpm range, which is particularly desirable insmall-volume engines. This effect results in particular from themulti-fluted, preferably double-fluted, design of the exhaust gas-driventurbo-charger, such that when the coupler is closed the single-flutedimpinging for low rpm ranges can be optimized and opened successivelyonly with increasing engine speed of the coupler.

In a further embodiment the bypass port is opened beyond the openposition with actuation of the coupler so that the boost pressure can berestricted. It is to be noted here that adjustment of the boost pressureratio is enabled both by a rise in throughput by opening of anotherflute and by a drop in the mass current by opening the bypass, by meansof only one servo component, the coupler.

Further advantageous embodiments of the invention will emerge fromsub-claims 2 to 20.

Preferred embodiments of the invention will now be explained hereinbelowwith reference to the accompanying diagrams, in which:

FIG. 1 is a longitudinal cross-section of an exhaust gas-driventurbo-charger with contour sleeve and coupler in the closed position,

FIG. 2a is a scaled-down illustration of the exhaust gas-driventurbo-charger according to claim 1,

FIG. 2b shows the exhaust gas-driven turbo-charger according to FIG. 2awith coupler in the open position,

FIG. 2c shows the exhaust gas-driven turbo-charger according to FIG. 2awith coupler in the bypass position,

FIG. 3a is a cutout longitudinal section of an exhaust gas-driventurbo-charger with sleeveless coupler control in the closed position,and

FIG. 3b shows the exhaust gas-driven turbo-charger according to FIG. 3awith coupler in the bypass position,

FIG. 1 illustrates a exhaust gas-driven turbo-charger having a turbine 2and a compressor 3 powered by turbine 2, both of which are designed in aradial structure. Turbine 2 and compressor 3 are mounted on a commonshaft 4.

Turbine 2 utilises the energy contained in the exhaust gas to drivecompressor 3 which sucks in fresh air and pushes pre-compressed air intothe cylinder of the diesel engine, not illustrated here. In terms offluid technics, exhaust gas-driven turbo-charger 1 is coupled to theengine only by the air and exhaust gas mass current. Its engine speed isdependent not on the engine speed, rather on the power-weight ratiobetween turbine 2 and compressor 3.

A double-fluted turbine housing 5 surrounds turbine wheel 6. Integralcomponents of turbine housing 5 are both afflux ports 7 a and 7 barranged axially at a distance from one another and whose outlets 8 aand 8 b concentrically surround wheel approach 9 inside turbine wheel 6almost over its entire circumference. Both afflux ports 7 a and 7 b areseparated from one another by a radially extending partition 10 ofturbine housing 5. The current of exhaust gas exiting from outlets 8 aand 8 b impacts wheel approach 9, which is formed by the radially outerends of blades 11 of turbine wheel 6, whereby its blank lends acylindrical outer contour to the wheel approach. Blades 11 exhibit acurved blank, such that the exhaust gas leaves turbine wheel 6 on adiameter lying radially further inwards. The exhaust gas flow thenenters downstream exhaust gas port 12 of radial turbine 2 which isformed by a tubular contour sleeve 13, arranged coaxially to axis 14 ofexhaust gas-driven turbo-charger 1. The downstream end of contour sleeve13 presents a curved blank, such that the contour sleeve conforms to thecurved section of blades 11. The external diameter of the cylindricalouter circumference of contour sleeve 13 approximately the same diameteras the diameter of wheel approach 9, such that contour sleeve 13 liesflush with wheel approach 9.

For opening and closing downstream afflux port 7 b or its outlet 8 b theradial turbine has an annular, axially displaceable coupler 15 which isillustrated in its closed position in FIG. 1 and FIG. 2a. Coupler 15,disposed coaxially to axis 14, encloses contour sleeve 13 concentricallyand slides on its cylindrical external profile in its adjustmentposition in an axial direction. For this purpose coupler 15 is coupledby its downstream end to a drive 16 controlled according to boostpressure. For sealing off downstream afflux port 7 b, coupler 15 has onits end on the afflux side a closure head 16 having a conical sealingsurface 17 a, which in turn cooperates with a conically formed sealingsurface 17 b of partition 10. In its closed position closure head 16completely covers over outlet 8 b, effectively preventing the escape ofexhaust gas from afflux port 7 b. In addition, closure head 16 exhibitsa cylindrical section connecting to sealing surface 17 a. Should the gasthroughput for maintaining a preset boost pressure ratio now beincreased, coupler 15 is displaced in a downstream direction, resultingin release of outlet 8 b and clearing the way for the exhaust gas flowto wheel approach 9. This open position is shown in FIG. 2b.

In order to avoid exceeding the highest permissible boost pressure withincreasing engine speed, the exhaust gas-driven turbo-charger exhibits abypass port 19 whose connection to both flutes joining up directly infront of wheel approach 9 is released by means of further downstreamdisplacement of coupler 15. In this bypass position of coupler 15illustrated in FIG. 2c its closure head 16 frees up a recess 20 a on thehousing side. For annular seal 21 to be flowed around downstream ofrecess 20 a in the direction of bypass port 19, coupler 15 also presentsa circular groove 22 downstream of closure head 16 so that bypass port19 is finally connected at least with the exhaust gas flow of affluxport 7 b by means of groove 22 and recess 20.

FIGS. 3a and 3 b illustrate an alternative embodiment of exhaustgas-driven turbo-charger 1 without the design of a contour sleeve. Thefunction of the contour sleeve is replaced here entirely by the tubulardesign of coupler 15, such that longitudinally displaceable coupler 15disposed coaxially also to axis 14 forms exhaust gas port 12.

Turbine wheel 6 is designed with a so-called ‘100% contour’, that is,wheel approach 9 extends essentially over the entire axial depth ofturbine wheel 6. Wheel approach 9 is disposed at a radial distanceopposite outlets 8 a and 8 b, as well as opposite a cylindricalsection—coupler guide 23. Coupler guide 23 exhibits a bushing 24 foraxially displaceable guiding of coupler 15 and for sealing. Asillustrated in FIG. 3, both the outer and the inner diameter ofsleeve-shaped coupler 15 is matched to the diameter of coupler guide 23and to the outer diameter of wheel approach 9 such that when the coupleris in its closed state closure head 16 of coupler 15 seals off bothafflux port 7 b or its outlet 8 b and tightly seals off gap 25 resultingfrom the radial clearance of wheel approach 9 from coupler guide 23. Inaddition to this, closure head 16 is essentially designed as the closurehead in FIG. 1, so that sealing surfaces 17 a and 17 b cooperate withone another and closure head 16 seals off outlet 8 b when the coupler isin the closed position, as is illustrated in FIG. 3a.

In the closed state coupler 15 covers over wheel approach 9 in an axialsection. With successive opening of coupler 15 in the downstreamdirection closure head 16 releases outlet 8 b, allowing the flow ofdownstream afflux port 7 b to impact turbine wheel 6. Likewise, the gapbetween wheel approach 9 and coupler guide 23 remains closed when outlet8 b is fully freed up by covering over of wheel approach 9. Only throughfurther downstream displacement of coupler 15 does the closure head freethe gap, so that a portion of the exhaust gas flow-the discharging-is nolonger discharged as illustrated in FIG. 1 around coupler 15, ratherinside the coupler.

In order to guarantee optimum impacting of wheel approach 9 bydownstream afflux port 7 a, closure head 16 presents a conicallytapering inlet 26, by means of which a dead normal path is avoided. Toensure imperviousness between turbine housing 5 and coupler 15 a pistonring cooperating tightly with coupler guide 23 is provided in thedownstream connection on the closure head. Haynes alloy is used asmaterial for this piston ring to guarantee the required elasticity inmaximum operating temperatures. For optimum combined effect betweenpiston ring 27 and bushing 24, the bushing is manufactured from thematerial Brico PMS 2600 which has not only the necessary temperature andcorrosion endurance, but also the lubrication capacity. The solid seatof bushing 24 is ensured by means of a press fit. In contrast to thecoupler illustrated in FIG. 1, the coupler according to FIGS. 3a and 3 bis designed from the material Brico PMS 2600 instead of the castingmaterial Inconell 713C. This effectively dispenses with the costlycasting process required for Inconell.

Legend  1 exhaust gas-driven turbo-charger  2 turbine  3 compressor  4shaft  5 turbine housing  6 turbine wheel  7a, b afflux port  8a, boutlet  9 wheel approach 10 partition 11 blade 12 exhaust port 13contour sleeve 14 axis 15 coupler 16 closure head 17a, b sealing surface18 drive 19 bypass port 20a, b recess 21 annular seal 22 groove 23coupler guide 24 bushing 25 gap 26 inlet 27 piston ring

What is claimed is:
 1. An exhaust gas-driven turbo-charger having anadjustable radial turbine which powers a compressor by way of a commonshaft, in which the turbine housing defines at least two afflux partsannularly encompassing the turbine wheel having outlets at least partlysurround the wheel approach of the turbine wheel and being axiallyoffset from each other, the turbo-charger including an annular, axiallydisplaceable coupler for selectively opening and closing the outlet ofat least one afflux port, wherein the turbine housing defines a bypasspart axially downstream from the afflux ports; and the coupler and theturbine housing cooperate to define a bypass flow path only when thecoupler is in a bypass position.
 2. The exhaust gas-driven turbo-chargeraccording to claim 1, wherein when the coupler is in said bypassposition the outlets are opened by the coupler.
 3. An exhaust gas-driventurbo-charger having an adjustable radial turbine which powers acompressor by way of a common shaft, in which the turbine housingdefines at least two afflux ports annularly encompassing the turbinewheel having outlets at least partly surround the wheel approach of theturbine wheel and being axially offset from each other, theturbo-charger including an annular, axially displaceable coupler forselectively opening and closing the outlet of at least one afflux port,wherein the two afflux ports are separated by an annular partitionhaving a radially inner end presenting an annular sealing surface; andthe coupler having an annular end sealing surface, wherein the sealingsurfaces are conical.
 4. The exhaust gas-driven turbo-charger accordingto claim 3, wherein the coupler extends axially over an axial section ofthe wheel approach when the coupler is closing at least one of theafflux ports.
 5. The exhaust gas-driven turbo-charger according to claim3, wherein the turbine housing defines a cylindrical guide surfacedownstream of the turbine, wherein the guide surface includes a bushingagainst which the coupler axially slides.
 6. The exhaust gas-driventurbo-charger according to claim 3, wherein said conical sealing surfaceof the coupler faces the afflux ports.
 7. The exhaust gas-driventurbo-charger according to claim 6, wherein said coupler defines aconically tapering inlet facing the wheel approach opposite said annularend sealing surface.
 8. An exhaust gas-driven turbo-charger having anadjustable radial turbine which powers a compressor by way of a commonshaft, in which the turbine housing defines at least two afflux portsannularly encompassing the turbine wheel having outlets at least partlysurround the wheel approach of the turbine wheel and being axiallyoffset from each other, the turbo-charger including an annular, axiallydisplaceable coupler for selectively opening and closing the outlet ofat least one afflux port, wherein the two afflux ports are separated byan annular partition having a radially inner end presenting an annularsealing surface; and the coupler having an annular end sealing surface,wherein the sealing surfaces are conical; in which the turbine housingdefines a cylindrical guide surface downstream of the turbine, whereinthe guide surface includes a bushing against which the coupler axiallyslides, and wherein the coupler includes a radial piston ring that bearsagainst said bushing in sealing relation.
 9. An exhaust gas-driventurbo-charger having an adjustable radial turbine which powers acompressor by way of a common shaft, in which the turbine housingdefines at least two afflux parts annularly encompassing the turbinewheel having outlets at least partly surround the wheel approach of theturbine wheel and being axially offset from each other, theturbo-charger including an annular, axially displaceable coupler forselectively opening and closing the outlet of at least one afflux port,wherein the turbine housing defines a bypass part axially downstreamfrom the afflux ports; and the coupler and the turbine housing cooperateto define a bypass flow path only when the coupler is in a bypassposition, wherein the bypass flow path includes a recess defined in thecoupler.
 10. An exhaust gas-driven turbo-charger having an adjustableradial turbine which powers a compressor by way of a common shaft, inwhich the turbine housing defines at least two afflux parts annularlyencompassing the turbine wheel having outlets at least partly surroundthe wheel approach of the turbine wheel and being axially offset fromeach other, the turbo-charger including an annular, axially displaceablecoupler for selectively opening and closing the outlet of at least oneafflux port, wherein the turbine housing defines a bypass part axiallydownstream from the afflux ports; and the coupler and the turbinehousing cooperate to define a bypass flow path only when the coupler isin a bypass position, wherein the bypass flow path is radially outboardof the coupler.
 11. An exhaust gas-driven turbo-charger having anadjustable radial turbine which powers a compressor by way of a commonshaft, in which the turbine housing defines at least two afflux partsannularly encompassing the turbine wheel having outlets at least partlysurround the wheel approach of the turbine wheel and being axiallyoffset from each other, the turbo-charger including an annular, axiallydisplaceable coupler for selectively opening and closing the outlet ofat least one afflux port, wherein the turbine housing defines a bypasspart axially downstream from the afflux ports; and the coupler and theturbine housing cooperate to define a bypass flow path only when thecoupler is in a bypass position, wherein disposed between the turbinehousing and the coupler is a seal which contacts the coupler in theclosed position, while a recess formed in the coupler breaks the contactof the seal, with the coupler in the bypass position, and unblocks theconnection to the bypass port.